docs: def get_zenith(self, channel=0) -> tuple:
          """Get the coordinates, in units, of the maximum in a channel.
  
          Parameters
          ----------
          channel : int or str (optional)
              Channel. Default is 0.
  
          Returns
          -------
          generator of numbers
              Coordinates in units for each axis.
          """
          # get channel
          if isinstance(channel, int):
              channel_index = channel
          elif isinstance(channel, str):
              channel_index = self.channel_names.index(channel)
          else:
              raise TypeError("channel: expected {int, str}, got %s" % type(channel))
          channel = self.channels[channel_index]
          # get indicies
          idx = channel.argmax()
          # finish
          return tuple(a[idx] for a in self._axes)